Zebetite

A zebetite, or zeebetite, in Metroid, is a life-support unit for Mother Brain. It can only be destroyed with missiles. Zebetites shrink as they are attacked, and eventually will completely disappear; but if the attack is broken off early, they will grow back. They are essentially a last line of defense, stalling Samus Aran on her path to Mother Brain while nozzles and rinkas attack.